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NCERT Class 10 Science Metals and Non-metals: In-text questions (page 49) Solutions
AI-written, checked on 23 Oct 2026
Solutions written by Shishya, checked — not the board's official answers
Step-by-step working for every question of In-text questions (page 49) in NCERT's Class 10 Science book, chapter “Metals and Non-metals”, written by Shishya. Each question is in our own short words; open the NCERT chapter for the exact wording and figures.
How these were checked: the solutions were drafted with AI and then read and corrected on 23 Oct 2026. Every numerical final answer is recomputed from the question's own numbers by a calculator check that runs before each release; proofs and explanations were read, not machine-checked. The NCERT textbook is the authority — if something here disagrees with it, follow the book.
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In-text (page 49) Q1
(i) Write the electron-dot structures of sodium, oxygen and magnesium. (ii) Show the formation of Na₂O and MgO by transfer of electrons. (iii) Which ions are present in these compounds?
- (i) Sodium (Na) has atomic number 11, so its electron configuration is 2, 8, 1; its electron-dot structure shows one valence electron.
- (i) Oxygen (O) has atomic number 8, so its electron configuration is 2, 6; its electron-dot structure shows six valence electrons.
- (i) Magnesium (Mg) has atomic number 12, so its electron configuration is 2, 8, 2; its electron-dot structure shows two valence electrons.
- (ii) In the formation of Na₂O, two sodium atoms each lose one electron to become Na⁺ ions, and one oxygen atom gains two electrons to become an O²⁻ ion.
- (ii) In the formation of MgO, one magnesium atom loses two electrons to become a Mg²⁺ ion, and one oxygen atom gains two electrons to become an O²⁻ ion.
- (iii) The ions present in sodium oxide (Na₂O) are sodium ions (Na⁺) and oxide ions (O²⁻).
- (iii) The ions present in magnesium oxide (MgO) are magnesium ions (Mg²⁺) and oxide ions (O²⁻).
Answer: (i) Na: 2,8,1; O: 2,6; Mg: 2,8,2; (ii) Na₂O forms via 2Na⁺ + O²⁻, MgO forms via Mg²⁺ + O²⁻; (iii) Na₂O contains Na⁺ and O²⁻, MgO contains Mg²⁺ and O²⁻
In-text (page 49) Q2
Why do ionic compounds have high melting points?
- Ionic compounds are made of positive and negative ions arranged in a regular lattice.
- These ions are held together by strong electrostatic forces of attraction.
- A large amount of heat energy is required to overcome these strong forces.
- Therefore, ionic compounds have high melting points.
Answer: Ionic compounds have high melting points because strong electrostatic forces hold the ions together in the lattice.
Other exercises in this chapter
- In-text questions (page 40) — 2 questions
- In-text questions (page 46) — 5 questions
- In-text questions (page 53) — 3 questions
- In-text questions (page 55) — 3 questions
- End-of-chapter exercises — 16 questions
← Metals and Non-metals: notes, practice and all exercises
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